Telephone-exchange system.



L. H. JOHNSON.

TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED MAR. n. ma.

1 ,230,582 Patented June 19, 1917.

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UNITED STATES" PATENT oruion.

LEWIS H. JOHNSON, OF BLOOMFIELD, JERSEY, ASSIGNOR, BY MESNE ASSIGN- MENTS, TO WESTERN ELECTRIC COMPANY, INCORPORATED, A CORPORATION OF NEW YORK.

TELEPHONE-EXCHANGE SYSTEM.

Specification of Letters Patent.

Patented June 19, 1917.

Application filed March 11, 1915. Serial No. 13,602;

such systems of the central energy type, the

object of this invention being to provide improved signaling means for such systems. In accordance with one feature of this 1nvention means are provided at the central station whereby after both receivers have been restored to the switchhooks either the calling or called subscriber may, by the subsequent removal of the receiver from the switchhook, cause the operation of recall signaling means at the central oflice, notifying the operator that this'subscriber desires.

to make another call. t

This invention is illustrated in the accompanying drawing, in which all apparatus is shown in its normal or unactuated condition.

There is shown in the drawing a telephone exchange system containing one embodiment of this invention and comprising the usual subscribers stations, A and B, and a cord circuit C- located at the central office for interconnecting the subscribers stations. It is believed that this invention will be fully understood from a description of the opera tion of the system shown in the drawing, and it will be so described.

Supposing subscriber A wishes to con.- verse with subscriber B. A removes the re ceiver from the switchhook, thereby completing a circuit from battery 5, through one winding of line relay 7, contact 8 of cutofi relay 9, line wires 10 and 11, contact 12 of cutoff relay 9 and the other winding of line relay 7 to battery 5. Current in this path actuates line relay 7, completing a circuit for line signal 13. The operator, observing the line signal 13, inserts the answering plug in the jack indicated by signal 13 and thereby completes a' circuit from battery 14, through the winding of relay 15, sleeve contacts of the answering plug and jack, and the winding of cutofi relay 9 to ground.

Current in this path actuates cutoif relay 9 which severe the circuit of the line relay 7, eifacing'line signal 13. Current in the last mentioned path also actuates relay 15, closing its contact 16. The closing of this contact would complete a circuit from battery 17, through supervisory signal 18,,contact 19 of relay 20 and contact-16 of relay 15 to ground, were it not for the fact that relay 20 is actuated upon the insertion of the answering plug over a circuit from battery 21, through one winding ofrelay 20, ring contacts of the answering plug and jack, line wires 10 and 11,tip contacts of the jack and answering plug and the other winding of relay 20 to ground. The operator now actuates listing key 25, connecting the operators telephone set to the line, and converses with the calling subscriber. Ascertaining that the number desired is that of subscribenB, the, operator touches the tip of the calling plug to the sleeve of the jack correspondlng to Bs line to determine the idlcor'busy condition thereof. If the line tests idle the calling plug is inserted into the jack, completing a circuit from battery 28. Relay 27 completes a circuit from bat-' tery 29, through supervisory signal 30, contact 31 of relay 32 and contact 33 of relay 27 to ground, operating supervisory signal 30. The actuation of cutofi'lrelay 28 cuts line relay 35 from line wires 36 and 37. The operator now restores listening key 25 to normal position and operates ringing key 38, connectingta source of ringing current to the ring side of the line, and ground to the tip sided Current flowing out over the line wires 36 and .37, operatesring'er 39 at stationwB. Subscriber B,- upon' removing thereceiver. from the s-witchhook, closes a path for direct .current from. battery 40 through thewinding of relay 32. Relay 32 operates, opening the circuit of supervisory signal 30. When listening key 25 was restored to normal its contact41 was closed, thereby completing a circuit from battery 17', through supervisorysignal 18, contact 42 of relay 20, contact 43 of relay 44, winding of relay 45, contact 41 of the listening key 25 and contact 16 of relay 15 to ground. Current in this pathactuates relay 45 which closes its contact 46, connecting relay 44 and battery 4'7 inseries' with relay 45': The actuation of relay 45, in connecting relay 44 in series therewith, also connects relay 44 in parallel with supervisory signal 18. The resistance of relay 45 is so high that when relay 44 and supervisory signal 18 are connected in parallel, and in series with relay 45, relay 44 will not operate. It is also to be observed that when either supervisory signal 18 or 30 are in series with relay 45 these signals are non-operative. The actuation of relay 32, in response to the removal of the receiver at station B from the switchhook closes its contact 48, thereby placing supervisory signal 30 in parallel with supervisory signal 18 and relay 44, and in series with relay 45. Subscribers A and B are now connected and the receivers at both substations are removed from the switchhooks.

Upon completion of the conversation, both subscribers restore the receivers to the switchhooks, whereupon relays 20 and 32 release, permittin supervisory signals 18 and 30 to operate to give disconnect signals. If the operator is not busy, the answering and calling plugs are removed from the jacks and all apparatus returns to normal. Suppose, however, that as is frequently the case during busy periods, the operator does not immediately take down the connection and suppose further that either subscriber A or subscriber B desires to immediately make another call. Assuming that subscriber A wishes to make another call, the receiver is removed from the switchhook, thereby causing supervisory signal 18 to intermittently flash, signifying to the operator that subscriber A desires another connection. The manner in which supervisory signal 18 is caused to flash will now be described. \Vhen both subscribers restore their receivers to the switchhooks, the release of relays 20 and 32 opens the circuits which were in parallel with relay 44, thereby permitting the operation of this relay over a circuit from battery 47, through the winding of relay 44, contact 46 and winding of relay 45, contact 41 of listening key 25 and contact 16 of relay 15 to ground. Current in this path actuates relay 44 which opens its contact 43 and closes its contact 49. Now, when subscriber A removes the receiver from the switchhook, relay 20 is actuated, opening contact 19 and closing contact 42. The closure of contact 42 completes a circuit from battery 17, through supervisory signal 18, contact 42 of relay 20, contact 49 of relay 44, and interrupter 50 to ground, causing supervisory signal 18 to flash intermittently to furnish a recall signal. The operator observing that supervisory signal 18 is fiashing,operates the listening key 25, connecting the op erators telephone set to theline. The operation of the listening key 25 opens contact 41, thereby releasing relays 44 and 45 and disconnecting the interrupter from the circuit including supervisory signal 18. The operator, ascertaining the number of the line desired by subscriber A, withdraws the calling plug and inserts it into the jack of the line wanted.

Should subscriber B be the one desiring another connection Bs receiver removed from the switchhook, causing supervisory signal 30 to flash in identically the same manner as supervisory signal 18 flashes when the receiver at substation A is removed from the switchhook. \Vhile in this description a number of batteries have been referred to, it is to be understood that a common battery may be substituted therefor, and such is the usual practice.

hat is claimed is:

1. A telephone exchange system comprising calling and called subscribers lines, a link circuit connecting said lines, a signaling device associated with the link circuit, interrupter mechansm, and means associated with the link circuit and controlled by the restoration of both receivers to the switchhooks and a subsequent removal of one receiver for including the interrupter mechanism in circuit with the signaling device.

2. A telephone exchange system comprising calling and called lines, a link circuit connecting said lines, a signaling device associated with the answering end of the link circuit, interrupter mechanism, and means associated with the link circuit and controlled by the restoration of both receivers to the switchhooks and a subsequent removal of the receiver of the calling subscribers station for including the interrupter mechanism in circuit with the signaling device.

3. A telephone exchange system comprising calling and called subscribers lines, a link circuit connecting said lines, a signaling device associated with each end of said link circuit, interrupter mechanism, and means associated with the link circuit and controlled by the restoration of both receivers to the switchhooks and subsequent removal of the receiver at the calling subscribers station for including the interrupter mechanism in circuit with the signaling de vice associated with the answering end and by a subsequent removal of the receiver at the called subscribers station for including the interrupter mechanism in circuit with the signaling device associated with the calling end.

4. In a telephone exchange system, calling and called subscribers lines, a link circuit for interconnecting said lines, a signaling device associated with the calling end of said link circuit, an interrupter associated with said link circuit, a local air cuit for said signaling device and said. interrupter open at two points, a relay actuated upon the restoration of both the calling and called subscribers receivers to the switchhooks for closing said local circuit at one point, and a relay actuated upon a subsequent removal of the called subscribers receiver for causing the final closure of said local circuit, wherebv said signaling device is caused to flash intermittently to give a recall signal.

5. A telephone exchange system comprising calling and called subscribers lines, a link circuit connecting said lines, a signaling device associated with the link circuit, interrupter mechanism, and a plurality of relays associated with the link circuit and controlled by the restoration of both receivers to the switchhooks and a subsequent removal of one receiver for including the interrupter mechanism in circuit with the signaling device.

6. A telephone exchange system comprising calling and called subscribers lines, a link circuit connecting said lines, a supervisory relay associated with the link circuit and controlled from a connected substation, a signaling device, an interrupter, a local series circuit for the signaling device and the interrupter open at two points, a relay energized upon the denergization of the supervisory relay for closing a break in the local circuit, and contacts of the supervisory relay included in the local circuit and engaged upon the subsequent energization thereof to close the other break.

7 A telephone exchange system comprising calling and called subscribers lines, a link circuit connecting said lines, a supervisory relay associated with the link circuit and controlled from the calling station, an answering supervisory signaling device, an interrupter, a local series circuit for the signaling device and the interrupter open at two points, a relay energized upon the deenergization of the supervisory relay for closing a break in the local circuit, and contacts of the supervisory relay included in the local circuit and engaged upon the subsequent energization thereof to close the other break.

8. A telephone exchange system comprising calling and called subscribers lines, a link circuit connecting said lines, a supervisory relay associated with the link circuit and controlled from a connected substation, a signaling device, an interrupter, a local circuit for the signaling device and the interrupter open at two points, a primary relay energized when the supervisory relay is energized, a secondary relay brought into circuit with the primary relay upon the energization thereof, and a short circuit about the secondary relay while the supervisory relay is energized, the deenergization of the supervisory relay removing the short circuit and permitting the energization of the secondary relay to close one break in the local circuit and the subsequent energization of the supervisory relay closing the other break in and completing the local circuit.

9. A telephone exchange system comprising calling and'called subscribers lines, a link circuit connecting said lines, a supervisory relay associated with the link circuit'and controlled from the calling station, a signaling device, an interrupter, a local circuit for the signaling device and the interrupter open at two points, a primary relay energized when the supervisory relay is energized, a secondary relay brought into circuit with the primary relay upon the energiza'tion thereof, and a short circuit about the secondary relay while the supervisory relay is energized, the denergization of the supervisory relay removing the short circuit and permitting the energization of the secondary relay to close one break in the local circuit and the subsequent ener gization of the supervisory relay closing the other break in and completing the local circuit.

10. A telephone exchange system comprising calling and called subscribers lines, a link circuit connecting said lines, a supervisory relay associated with each end of the link circuit and controlled from the respective connected stations, a signaling device, an interrupter, a local circuit for the signaling device and the interrupter open at two points, a primary relay energized when either one of the supervisory relaysis energ'ized, a secondary relay brought into circuit with the primary relay upon the energization thereof, a short circuit about the secondary relay while the supervisory re lays are energized, the deenergization of the supervisory relays removing the shortcircuit and permitting the energization of the secondary relay to close one break-in the local circuit and the subsequent energization of either supervisory relay closing the other break in and completing the local circuit.

11. In a telephone exchange system, calling and called subscribers lines, a link circuit connecting said lines, a relay associated with the link circuit and adapted to be controlled from one of the connected stations, a signaling device associated with the link circuit and controlled by the relay, interrupter mechanism, and a second relay jointly controlled from both connected stations for connecting the interrupter mechanism in circuit with the signaling device.

12. In a telephone exchange system, calling and called subscribers lines, a link circuit connecting said lines, a relay associated with the link circuit and adapted to be controlled from the connected calling station, a signaling device associated with the answering end of the link circuit and my name this 10th day of March A. D., controlled by the relay, interrupter mecha- 1915. nism, and a second relay jointly controlled from both connected stations for connecting LEW'IS H. JOHNSON.

the interrupter mechanism in circuit with Witnesses: the signahng device. E. EDLER,

In witness whereof, I hereunto subscrlbe K. L. STAI-IL.

Copies of this patent may be obtained for five cents each, by addressing the Commissioner of Patents. Washington, D. C. 

